<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		
		<style type="text/css">
			:root {
				font-size: 50px;
				margin: 0;
			}
			
			span {
				background-color: gray;
				color: #ffffff;
			}
			
			div {
				width: 3ch;
				/* background-color: #000000; */
				background: #000000;
				height: 60px;
				/* border: 2px #0000FF solid; */
			}
		</style>
	</head>
	<body>
		<!-- ch    1ch 等于当前字体族的数字0 的宽度 -->
		<span>000</span>
		<div></div>
	</body>
</html>
